Seems the lower grey ring is fixed solid to the chest harness thing, and the upper grey ring to the helmet, but the rings aren't supposed to touch, despite appearances. Instead, there's an inner ring to the lower one, and this inner ring is hanging from a soft piece of cloth that is fixed to the interior of the chest harness. The helmet clicks on to the inner ring, and the head can thus be turned with the helmet, rather than within it.
The outer lower ring is what makes this look confusing, as it appears as if the helmet should click on to that and then stay fixed, NASA style. But it's not supposed to work that way. Perhaps the outer ring is just for decoration, perhaps it protects the soft material of the inner setup in practice. Looks reasonably cool - but admittedly also confusing.
Timo Saloniemi